Mostly poison
Barn owls eat mice, rats and various other small mammals, helping to keep the rodent population under control as nature intended. During outbreaks of the rat / mice population, Barn owls will breed several times during the year, thus acting as a natural pest control.
Yes, a good one. Barn owls, all owls for that matter, are rodent eaters. That is, they feast on mice, rats, squirrels, chipmunks, and just about any other critter that can and often do have a negative affect on humans.
When the barn owls eat a rodent they spit out the bones and fur so the moths eat the owl pellets from the barn owls
Barn owls are very helpful predators. They can kill tons of rodents a year which can help stop a rodent infestation.
There will be a slight decline in the Barn Owl population. This is because voles have the highest occurence and when that occurence disappears, the Barn Owls will have harder time finding food and won't be as easy.
I assume you mean "Why are barn owls named Barn owls?", and if that's the case then I can answer that. Barn owls are called Barn owls because they roost in Barns and churches, and there's already a Church owl.
Sadly, yes. Unfortunately mainly due to habitat being destroyed and harmful rodent poison which can harm the owls too.
Barn Owl populations are believed to be on the decline, but they were not on the 2012 watch list. It is difficult to keep track of Barn Owls due to their secretive nature.
yes
make sure the cows are in the barn
Barn owls are one of the few owls that are easily attracted to nest boxes. Such boxes should be rather large--about 16w x 16 h x 20 deep or larger. The entrance hole diameter should be between 5 and 6 inches, and the box should either be attached to an outbuilding, hung in a tree, or mounted on a pole. Eight to ten feet up is adequate. The owls are excellent at finding cavitiies--it is the dark entrance hole that attracts their curiosity. There are plenty of barn owl nest box plans on the internet, and a couple of companies make and sell them. There is a new, lightweight barn owl box on the market made out of molded plastic that is easy to install. It is made by The Barn Owl Box Company. Barn owls are excellent for natural rodent control on private property, farms, etc. Be sure to read more about barn owl biology on the internet.
Predators of barn owls include: house and feral cats, Great Horned Owls, Eurasian Eagle-owls, large American opossums, raccoons, hawks and eagles.